KR102416262B1 - Method and apparatus for transmitting signal in communication system - Google Patents

Abstract

The present disclosure relates to a 5G or pre-5G communication system for supporting a higher data rate after a 4G communication system such as LTE. A method proposed in an embodiment of the present disclosure includes; A method for transmitting a reference signal in a communication system, comprising: transmitting the reference signal generated based on a pre-generated transmission matrix, wherein the pre-generated transmission matrix includes zero elements and non - One reference matrix including zero elements (non-zero elements) is generated by repeating a predetermined number, and the reference sequence is the non-zero element included in the transmission pre-generated matrix. are assigned a specific sequence, wherein one of a plurality of elements included in the reference matrix is assigned to each of the non-zero elements included in a first column in the transmission matrix, and one element included in the reference sequence An element cyclically shifted from is allocated to each of the non-zero elements included in the second column in the transmission matrix positioned at a predetermined column interval from the first column.

Description

Method and apparatus for transmitting a signal in a communication system

The present disclosure relates to a method and apparatus for transmitting a signal for channel estimation in a communication system.

Efforts are being made to develop an improved 5G (5 ^th -Generation) communication system or pre-5G communication system to meet the increasing demand for wireless data traffic after commercialization of the 4G (4 ^th -Generation) communication system. . For this reason, the 5G communication system or the pre-5G communication system is called a system after the 4G network (beyond 4G network) or the LTE system (post LTE).

In order to achieve a high data rate, the 5G communication system is being considered for implementation in a very high frequency (mmWave) band (eg, such as a 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, in the 5G communication system, beamforming, massive multi-input multi-output (massive MIMO), and all-dimensional multiple input/output ( Full dimensional MIMO: FD-MIMO), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, for network improvement of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud radio access network: cloud RAN), an ultra-dense network (ultra-dense network) , device to device communication (D2D), wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), and interference cancellation Technology development is underway.

In addition, in the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), which are advanced coding modulation (ACM) methods, and advanced access technologies such as filter bank multi carrier (FBMC), NOMA (non orthogonal multiple access), and sparse code multiple access (SCMA) are being developed.

The SCMA has received attention as a multiple access technology capable of supporting a plurality of terminals in an Internet of things (IoT) environment by sharing and using time-frequency resources. However, the results so far are the results of assuming accurate synchronization and accurate channel estimation, and studies on channel estimation and synchronization methods in a communication system based on SCMA are lacking. In addition, when transmitting data in an SCMA-based communication system, N _data resource elements (REs) are used based on one orthogonal frequency division multiplexing (OFDM) symbol, whereas channel estimation is performed. For this reason, when a demodulation reference signal (DMRS) is used, N _pilot REs should be used as a reference signal based on one OFDM symbol. Here, the N _data and N _pilot is determined as in Equation 1 below.

<Equation 1>

은 주파수 대역에서의 데이터 전송에 사용되는 서브캐리어(subcarrier)의 길이에 해당하며, 하나의 RE당 심볼 전력을 1로 가정하였다. SCMA를 기반으로 하는 통신 시스템에서 기존의 DMRS를 이용한 채널 추정 시 파일럿으로 사용되는 RE의 수가 데이터 전송 시 필요한 RE의 수에 대비하여

배 증가하게 된다. 또한 주파수에 따라 변화하는 주파수 선택적인 페이딩 채널(frequency selective fading channel)에서 기존의 DMRS는 직교성이 유지되지 않아 채널 추정 성능이 상당히 열화 하게 된다. here,

corresponds to the length of a subcarrier used for data transmission in a frequency band, and it is assumed that symbol power per one RE is 1. In the SCMA-based communication system, the number of REs used as pilots when estimating channels using the existing DMRS prepares for the number of REs required for data transmission.

will increase twice In addition, in a frequency selective fading channel that changes according to frequency, the conventional DMRS does not maintain orthogonality, so that the channel estimation performance is significantly deteriorated.

Therefore, there is a need for a method for generating and transmitting/receiving a DMRS for efficiently performing channel estimation in an SCMA-based communication system.

An embodiment of the present disclosure provides a method and apparatus for generating and transmitting and receiving a signal for channel estimation in a communication system.

In addition, an embodiment of the present disclosure provides a method and apparatus for generating and transmitting and receiving a signal having a sparse code characteristic in a communication system.

Another embodiment of the present disclosure provides a method and apparatus for generating and transmitting/receiving a signal for maintaining orthogonality in a frequency-selective fading channel in a communication system.

A method proposed in an embodiment of the present disclosure includes; A method of transmitting a reference signal in a communication system, comprising: transmitting the reference signal generated based on a transmission matrix, wherein the transmission matrix includes zero elements and non-zero elements zero elements) is generated by iterating a predetermined number of times, the reference sequence is allocated to the non-zero elements included in the transmission matrix, and one of the plurality of elements included in the reference matrix is In the transmission matrix, an element allocated to each of the non-zero elements included in a first column in the transmission matrix and cyclically shifted from one element included in the reference sequence is located at a predetermined column interval from the first column. It is characterized in that it is assigned to each of the non-zero elements included in the second column.

In addition, the method proposed in an embodiment of the present disclosure is; A method for receiving a reference signal in a communication system, comprising: receiving the reference signal generated based on a transmission matrix, wherein the transmission matrix includes zero elements and non-zero elements zero elements) is generated by iterating a predetermined number of times, the reference sequence is allocated to the non-zero elements included in the transmission matrix, and one of the plurality of elements included in the reference matrix is In the transmission matrix, an element allocated to each of the non-zero elements included in a first column in the transmission matrix and cyclically shifted from one element included in the reference sequence is located at a predetermined column interval from the first column. It is characterized in that it is assigned to each of the non-zero elements included in the second column.

In addition, an apparatus proposed in an embodiment of the disclosure includes; An apparatus for transmitting a reference signal in a communication system, comprising: at least one processor that controls to transmit a reference signal generated based on a transmission matrix, and transmits the reference signal, the transmission matrix comprising: element) and a reference matrix including non-zero elements (non-zero elements) is generated by repeating a predetermined number, the reference sequence is allocated to the non-zero elements included in the transmission matrix, the One of the plurality of elements included in the reference matrix is allocated to each of the non-zero elements included in the first column in the transmission matrix, and the element cyclically shifted from one element included in the reference sequence is from the first column. It is characterized in that it is assigned to each of the non-zero elements included in the second column in the transmission matrix positioned at a predetermined column interval.

In addition, an apparatus proposed in an embodiment of the disclosure includes; An apparatus for receiving a reference signal in a communication system, comprising: a control to receive the reference signal generated based on a transmission matrix; and at least one processor configured to receive the reference signal, the transmission matrix comprising: a zero element ( zero elements) and a reference matrix including non-zero elements (non-zero elements) is generated by repeating a predetermined number, and a reference sequence is allocated to the non-zero elements included in the transmission matrix, One of the plurality of elements included in the reference matrix is allocated to each of the non-zero elements included in a first column in the transmission matrix, and an element cyclically shifted from one element included in the reference sequence is the first column It is characterized in that it is assigned to each of the non-zero elements included in the second column in the transmission matrix located at a predetermined column interval from .

Other aspects, benefits and key features of the present disclosure will become apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings, which discloses preferred embodiments of the present disclosure.

Before processing the detailed description part of the present disclosure, it may be effective to establish definitions for specific words and phrases used throughout this patent document: the terms "include" and " "comprise" and its derivatives mean inclusive indefinitely; the term “or” is inclusive and means “and/or”; The phrases "associated with" and "associated therewith" and their derivatives include, be included within, and interconnected with ( interconnect with, contain, be contained within, connect to or with, couple to or with ), be communicable with, cooperate with, interleave, juxtapose, be proximate to, and likely to means to be bound to or with, to have, to have a property of, etc.; The term "controller" means any device, system, or part thereof that controls at least one operation, such a device being hardware, firmware or software, or some combination of at least two of said hardware, firmware or software. can be implemented in It should be noted that the functionality associated with any particular controller may be centralized or distributed, and may be local or remote. Definitions for specific words and phrases are provided throughout this patent document, and those of ordinary skill in the art will in many, if not most cases, apply such definitions to conventional as well as conventional, as well as to words and phrases defined above. It should be understood that this also applies to future uses of the phrases.

1 is a view showing a communication system to which an embodiment of the present disclosure is applied;
2 is a diagram illustrating a method of generating a signal in a communication system according to an embodiment of the present disclosure;
3 is a diagram illustrating an example of a factor graph matrix generated by a signal generating apparatus according to an embodiment of the present disclosure;
4 is a diagram illustrating an example of an extended factor graph matrix generated by a signal generating apparatus according to an embodiment of the present disclosure;
5 and 6 are diagrams showing examples of allocating a ZC sequence to an extended factor graph matrix in a signal generating apparatus according to an embodiment of the present disclosure;
7 is a diagram illustrating an example of an algorithm for generating a signal in a communication system according to an embodiment of the present disclosure;
8 is a diagram illustrating an internal configuration of a signal generating apparatus performing an operation for generating a signal in a communication system according to an embodiment of the present disclosure;
9 and 10 are diagrams showing an example of comparing the results of channel estimation using DMRS generated in each of the prior art and an embodiment of the present disclosure;
11 is a diagram illustrating a structure of a DMRS generated according to an embodiment of the present disclosure and an example of a structure of a DMRS generated according to the prior art;
12 is a diagram illustrating an example of comparing a result of estimating a channel using DMRS generated in each of the prior art and each of the embodiments of the present disclosure according to a channel environment;
It should be noted that throughout the drawings, like reference numerals are used to denote the same or similar elements, features, and structures.

BRIEF DESCRIPTION OF THE DRAWINGS The following detailed description with reference to the appended drawings will assist in a comprehensive understanding of various embodiments of the present disclosure, which are defined by the claims and their equivalents. While the following detailed description contains various specific details for the purpose of understanding it, these will be regarded as merely examples. Accordingly, those skilled in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

The terms and words used in the following detailed description and claims are not limited to the literal meaning, but are merely used to enable a clear and consistent understanding of the present disclosure by the inventor. Accordingly, for those skilled in the art, the following detailed description of various embodiments of the present disclosure is provided for illustrative purposes only, and defines the present disclosure as defined by the appended claims and their equivalents. It should be clear that it is not provided to do so.

In addition, it will be understood that singular expressions such as "a" and "above" include plural expressions in this specification, unless explicitly indicated otherwise. Thus, in one example, a “component surface” includes one or more component representations.

Also, terms including an ordinal number, such as first, second, etc., may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

In addition, the terminology used herein is used only to describe specific embodiments, and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms such as those defined in a commonly used dictionary should be understood to have a meaning consistent with the meaning in the context of the related art.

1 shows a communication system to which an embodiment of the present disclosure is applied.

Referring to FIG. 1 , a communication system 100 provides various communication services such as voice and packet data, and includes at least one base station 110 . Each base station 110 provides a communication service for a specific cell (cell) (150a, 150b, 150c). And one base station 110 may be in charge of a plurality of cells. In an embodiment of the present disclosure, the base station 110 refers to a transceiver entity that performs information and control information sharing with a terminal for cellular communication, and includes a base station and a base transceiver system (BTS). ), an access point (access point), a femto base station, a home base station (home nodeB), or other terms such as a relay node (relay node) may be called. In addition, the cell is meant to encompass various coverage areas such as megacells, macrocells, microcells, picocells, and femtocells.

The at least one terminal 120 may be fixed or mobile, and may include a mobile station, a mobile terminal, a user terminal, a subscriber station, and a wireless device. , may be referred to as another term such as a wireless modem or a wireless device.

In the communication system 100, it is necessary to estimate an uplink or downlink channel for data transmission/reception, system synchronization acquisition, channel information feedback, and the like. A process of reconstructing a transmission signal by compensating for signal distortion caused by a sudden change in the channel environment is called channel estimation. In addition, it is also necessary to measure the channel state of the cell to which the terminal 120 belongs or another cell. In general, a reference signal (RS) known to the terminal 120 and the base station 110 may be used for channel estimation or channel state measurement. Here, the reference signal may be allocated to all subcarriers or may be allocated between subcarriers for transmitting data. In particular, there is DMRS as a reference signal used in uplink for channel estimation in a communication system, and for transmission of a physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) Since only channel information of the corresponding frequency band is required, the DMRS is transmitted with the length of the corresponding frequency band. Hereinafter, it will be described on the assumption that the reference signal is a DMRS in the embodiment of the present disclosure, but it goes without saying that the embodiment of the present disclosure may be applied to other reference signals using the same structure or sequence as the DMRS.

The DMRS is generally transmitted in sequence. The sequence may be a sequence having excellent correlation properties. For example, a sequence having excellent correlation properties includes a zadoff-chu (ZC) sequence. Accordingly, the DMRS may be transmitted based on the ZC sequence shown in Equation 2 below.

<Equation 2>

Here, the ZC sequence of the base band has a characteristic that is completely orthogonal to the ZC sequence on which the cyclic shift is performed.

만큼 위상 변화시켜 새로운 시퀀스로 생성할 수 있다. 이에 한 단말에 대해서 공간 멀티플렉싱(spatial multiplexing)을 사용하는 경우 또는 한 셀 내에서 동일한 자원을 할당 받은 단말들에게 직교하는 참조 신호를 제공하기 위해 기저 ZC 시퀀스의 위상 변화를 적용하게 된다. 통신 시스템에서 상기 직교하는 참조 신호를 사용하기 위해서는 수신신호가 시간 정렬 (timing alignment)되어 수신되어야 하며, 채널의 주파수 응답이 DMRS를 전송한 주파수 대역 내에서 일정하게 유지되어야 한다. For example, in a communication system, a terminal or a base station transmits a baseband ZC sequence on a frequency

A new sequence can be created by changing the phase as much as possible. Accordingly, when spatial multiplexing is used for one terminal or to provide an orthogonal reference signal to terminals allocated the same resource within one cell, a phase change of the base ZC sequence is applied. In order to use the orthogonal reference signal in a communication system, the received signal must be received with timing alignment, and the frequency response of the channel must be kept constant within the frequency band in which the DMRS is transmitted.

Accordingly, an embodiment of the present disclosure proposes a method of generating an extended DMRS using a sparse code structure of data in order to efficiently perform channel estimation in an SCMA-based communication system. And the DMRS generated as in the embodiment of the present disclosure is transmitted to the receiving device through the transmitting device. Since the method of transmitting and receiving the DMRS from the transmitting device to the receiving device through the transmitting device is the same as the method of transmitting and receiving a signal in the prior art, the method for transmitting and receiving a signal will not be described in detail below. That is, below, a method for generating a DMRS in the signal generating apparatus according to an embodiment of the present disclosure will be described in detail.

2 illustrates a method of generating a signal in a communication system according to an embodiment of the present disclosure. Here, the method for generating a signal in a communication system according to an embodiment of the present disclosure may be generated by an apparatus for generating a signal included in each of the at least one base station 110 and the terminal 120 included in the communication system. . Hereinafter, for convenience of description, the device for generating the signal will be defined as a signal generating device.

Referring to FIG. 2 , the signal generating apparatus generates one factor graph matrix according to parameters used for channel estimation in an SCMA-based communication system ( 201 ). Here, the parameter may be received from another entity or stored in advance therein. And the parameter is a code length (K) used in a communication system based on SCMA, the number of non-zero symbols (N), and the maximum number of accessible terminals in a communication system based on SCMA ( J). In this case, J may be determined according to the relationship between K and N.

3 shows an example of a factor graph matrix generated by the signal generating apparatus according to an embodiment of the present disclosure, wherein the signal generating apparatus is similar to FIG. 3 when the parameters K=4, N=2, and J=6 You can create the same factor graph matrix. Here, the number of columns of the factor graph matrix corresponds to the code length, and the number of rows in the factor graph matrix corresponds to the maximum number of accessible terminals.

Next, in order to generate an extended DMRS having a sparse code structure, the signal generating apparatus determines the number of repetitions Q for repeating the generated one factor graph matrix ( 203 ). Here, the number of repetitions Q should be determined to satisfy the condition of Equation 3 below.

<Equation 3>

Here, d _f denotes the number of signals simultaneously transmitted and received in one tone included in the factor graph matrix. Here, the signal may be a signal transmitted and received by the terminal. Here, the one tone corresponds to one element included in a row of the factor graph matrix.

(tones)로 확장된 팩터 그래프 행렬을 생성한다(205). Thereafter, the signal generating apparatus repeats the one factor graph matrix Q times to obtain a total length

A factor graph matrix extended to (tones) is generated (205).

4 shows an example of an extended factor graph matrix generated by a signal generating apparatus according to an embodiment of the present disclosure, wherein the signal generating apparatus includes parameters K=4, N=2, J=6, Q=3, When L=12, an extended factor graph matrix as shown in FIG. 4 may be generated.

로 구성되는 ZC 시퀀스를 아래 <수학식 4>와 같이 생성한다(207).and the signal generating device has a length for applying to the extended factor graph matrix.

A ZC sequence composed of , is generated as shown in Equation 4 below (207).

<Equation 4>

Here, the length Q is set to a value equal to the number of times Q the factor graph matrix is repeated.

The signal generating apparatus allocates the generated ZC sequence in consideration of zero elements in the extended factor graph matrix in order to maintain orthogonality between terminals in the DMRS of length L ( 209 ). At this time, one element of the plurality of elements included in the ZC sequence is allocated to each of the non-zero elements included in one column in the extended factor graph matrix, and included in one column in the pre-generated matrix. An element cyclically shifted from the one element included in the ZC sequence is allocated to each of the non-zero elements and a non-zero element positioned at a predetermined column interval. From this, orthogonality may be maintained between non-zero elements included in the extended factor graph matrix. Accordingly, the signal generating apparatus may generate a DMRS of length L having a sparse code structure ( 211 ).

As an example, FIGS. 5 and 6 show examples of allocating a ZC sequence to an extended factor graph matrix in a signal generating apparatus according to an embodiment of the present disclosure. The signal generating apparatus considers the zero element included in the extended factor graph matrix when the parameters K=4, N=2, J=6, Q=3, and L=12 as shown in FIG. 5, and expands the factor graph matrix ZC sequence can be assigned to And the signal generating apparatus considers the zero element included in the extended factor graph matrix when the parameters K=5, N=2, J=10, Q=4, L=20 as shown in FIG. 6, and expands the factor graph A ZC sequence can be assigned to a matrix.

Accordingly, as shown in FIGS. 5 and 6, each of the non-zero elements included in one column in the extended factor graph matrix is assigned one element among a plurality of elements included in the ZC sequence, It is confirmed that the element cyclically shifted from the one element included in the ZC sequence is assigned to each of the non-zero elements included in one column in the extended factor graph matrix and the non-zero element positioned at a predetermined column interval. can Here, in FIGS. 5 and 6 , the predetermined column interval is 4 as an example.

Accordingly, it is possible to allocate a corresponding DMRS to each terminal based on the extended DMRS having a sparse code structure from the signal generation method described with reference to FIGS. 2 to 6 . That is, the DMRS may be allocated to each of the plurality of terminals for each tone having the same overlapping pattern in the extended DMRS having a sparse code structure according to an embodiment of the present disclosure. Therefore, since an extended DMRS having a sparse code structure is generated by cyclically shifting the base ZC sequence according to an embodiment of the present disclosure, tones overlapping in the same pattern maintain orthogonality, which maintains orthogonality in the overall DMRS. In addition, the extended DMR having a sparse code structure generated according to an embodiment of the present disclosure is applicable in frequency and time resources.

The method for generating a signal according to an embodiment of the present disclosure described above based on FIGS. 2 to 6 may be implemented with the algorithm shown in FIG. 7 . 7 shows an example of an algorithm for generating a signal in a communication system according to an embodiment of the present disclosure, and shows an algorithm for generating an extended DMRS that maintains orthogonality between terminals using a ZC sequence.

2 and 7 have been described with respect to a method of generating a signal for channel estimation in a communication system according to an embodiment of the present disclosure. Next, with reference to FIG. 8 , a channel in a communication system according to an embodiment of the present disclosure is described. An internal structure of a channel estimator generating a signal for estimation will be described.

8 is a view showing an internal configuration of a signal generating apparatus that performs an operation of generating a signal in a communication system according to an embodiment of the present disclosure. Here, the signal generating apparatus may be included in each of the at least one base station 110 and the terminal 120 .

Referring to FIG. 8 , the signal generating apparatus 800 includes a controller 801 , a transmitter 803 , a receiver 805 , and a storage 807 .

The control unit 801 controls the overall operation of the signal generating apparatus 800 , and in particular, controls an operation related to the signal generating operation according to an embodiment of the present disclosure. Since the operation related to the operation of generating a signal according to an embodiment of the present disclosure is the same as described with reference to FIGS. 2 to 6 , a detailed description thereof will be omitted herein.

The transmitter 803 receives various signals and various messages from other entities included in the communication system under the control of the controller 801 . Here, since the various signals and various messages received by the transmitter 803 are the same as those described with reference to FIGS. 2 to 6 , a detailed description thereof will be omitted.

In addition, the receiver 805 receives various signals and various messages from other entities included in the communication system under the control of the controller 801 . Here, since the various signals and various messages received by the receiver 805 are the same as those described with reference to FIGS. 2 to 6 , a detailed description thereof will be omitted.

The storage unit 807 stores a program and various data related to an operation related to an operation for generating a signal according to an embodiment of the present disclosure performed by the signal generating apparatus 800 under the control of the controller 801 . do. In addition, the storage unit 807 stores various signals and various messages received by the receiving unit 805 from the other entities.

Meanwhile, in FIG. 8 , the signal generating apparatus 800 is implemented as separate units such as the control unit 801 , the transmission unit 803 , the reception unit 805 and the storage unit 807 . Of course, the signal generating apparatus 800 may be implemented in an integrated form of at least two of the controller 801 , the transmitter 803 , the receiver 805 , and the storage 807 . Also, it goes without saying that the signal generating apparatus 800 may be implemented with one processor.

When channel estimation is performed using the extended DMRS having a sparse code structure generated by the signal generating apparatus according to an embodiment of the present disclosure, when channel estimation is performed using the DMRS generated by the prior art In comparison, it is possible to reduce calculation complexity for channel estimation and a mean square error (MSE) for channel estimation.

로 감소함에 따라 곱셈 계산에 대한 복잡도가 K/N배 감소하게 된다. 일 예로, 파라미터 K=4, N=2, J=6 일 때 데이터 길이 L=12인 sparse code 구조를 갖는 확장된 DMRS를 이용하여 채널 추정을 수행하면, 종래 기술 대비 곱셈 계산에 대한 복잡도가 2배 감소함을 확인 할 수 있다. When channel estimation is performed by a dispreading method using a DMRS having a length L generated by the prior art, the complexity of the multiplication calculation becomes L, but the sparse code structure generated according to an embodiment of the present disclosure When channel estimation is performed using the extended DMRS with

As it decreases, the complexity of the multiplication calculation is reduced by K/N times. For example, when channel estimation is performed using an extended DMRS having a sparse code structure having a data length of L=12 when parameters K=4, N=2, and J=6, the complexity of multiplication calculation is 2 compared to the prior art. It can be seen that the reduction is doubled.

And, as an example, in FIG. 9 , in the case of K=4, N=2, and J=6 in a communication system based on SCMA in FIG. 9 , MSE in the case of performing channel estimation using DMRS generated by the prior art and the present disclosure MSE in the case of performing channel estimation using the extended DMRS having a sparse code structure according to the embodiment of

9 and 10 show an example of comparing a result of channel estimation using DMRS generated in each of the prior art and an embodiment of the present disclosure.

이 된다. 따라서 동일한 비교를 위해, 본 발명의 실시 예에 따라 생성된 확장된 DMRS와 종래 기술에 의해 생성된 DMRS에서, (c)와 같이 전송 전력을 동일하게 L로 고정하면 톤당 전송 전력은 K/N배 증가함을 확인할 수 있다.Referring to FIGS. 9A and 9B , a non-zero element configured in a DMRS generated according to the prior art is compared with a non-zero element configured in an extended DMRS generated according to an embodiment of the present disclosure. Then, it can be confirmed that the number of non-zero elements configured in the extended DMRS generated according to an embodiment of the present disclosure is reduced compared to the number of non-zero elements configured in the DMRS generated by the prior art. As such, as the number of non-zero elements included in the extended DMRS generated according to an embodiment of the present disclosure decreases compared to the prior art, it can be confirmed that the transmit power for each tone increases. When the transmission power per tone is 1 in the DMRS included in the length L generated by the prior art, L, which is the total number of REs, becomes the total transmission power. On the other hand, in the case of the extended DMRS generated according to an embodiment of the present disclosure, assuming that the transmit power per tone is 1, the total transmit power is the number of REs.

becomes this Therefore, for the same comparison, in the extended DMRS generated according to the embodiment of the present invention and the DMRS generated by the prior art, if the transmission power is fixed to L as in (c), the transmission power per tone is K/N times increase can be seen.

In FIG. 10, it is assumed that the received signal is time-aligned in the base station. In addition, the channel is a Rayleigh block fading channel, case 1 (case I) is a case where the channel is constant for 1 RB, that is, 12 tones, and case 2 (case II) is a case where the channel is constant for 2 RBs. Here, a despreading method is used as the channel estimation method. In such a condition, as shown in FIG. 10 , the MSE performance in the case of performing channel estimation using the extended DMRS generated according to the embodiment of the present disclosure performs channel estimation using the DMRS generated by the prior art. It can be confirmed that it is the same as in the case of As shown in FIG. 9 , it is confirmed that the transmit power per tone in the extended DMRS having the sparse code structure generated according to the embodiment of the present disclosure increases, but as the non-zero element decreases, eventually the gain regarding despreading becomes the same. can

11 shows an example of a structure of a DMRS generated according to an embodiment of the present disclosure and a structure of a DMRS generated by the prior art, with parameters K=4, N=2, J=6, and active (Active) ) assumes the number of terminals is 3.

As shown in FIG. 11 , when the number of active terminals is small, interference is reduced due to increased transmission power per tone and a sparse code structure, so that channel estimation for each tone is possible with higher accuracy than in the prior art in a frequency-selective fading channel.

12 shows an example of comparing a result of channel estimation using DMRS generated in each of the prior art and each of the embodiments of the present disclosure according to a channel environment.

Referring to FIG. 12 , MSE performance of channel estimation was compared using DMRS generated in the prior art and each of the embodiments of the present disclosure for a pedestrian (pedestrian: Ped) channel and a vehicle (vehicular) channel. In addition, channel estimation was performed by a despreading method using the DMR generated by the prior art, and a despreading method is used for tones having interference due to a sparse code structure in the DMRS generated according to an embodiment of the present disclosure. For tones without interference, channel estimation was performed using the LS method for fine tuning. As shown in FIG. 12 , when channel estimation is performed using the DMRS generated according to an embodiment of the present disclosure, there is a significant performance gain for MSE compared to when channel estimation is performed using the prior art. can be checked

Therefore, in a communication system based on SCMA, channel estimation is performed using extended DMRS having a sparse code structure generated according to an embodiment of the present disclosure in not only a frequency flat fading channel but also a frequency selective fading channel, It is predicted that effective channel estimation for each tone will be possible.

Meanwhile, although specific embodiments have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments and should be defined by the claims described below as well as the claims and equivalents.

Claims (36)

A method for transmitting a reference signal in a communication system, comprising:
Transmitting the reference signal generated based on a transmission matrix,
The transmission matrix is generated by repeating a reference matrix including zero elements and non-zero elements by a predetermined number, and the reference sequence includes the non-zero elements included in the transmission matrix. - assigned to zero elements,
One of the plurality of elements included in the reference matrix is allocated to each of the non-zero elements included in a first column in the transmission matrix, and an element cyclically shifted from one element included in the reference sequence is the first column and each non-zero element included in the second column in the transmission matrix positioned at a predetermined column interval from .
The method of claim 1, wherein the reference matrix is
The code length used in the communication system, the number of non-zero symbols, the maximum number of accessible terminals in the communication system, the number of elements included in rows of the reference matrix corresponding to the code length, and the maximum accessible terminal The signal transmission method, characterized in that generated based on the number of elements included in the columns of the reference matrix corresponding to .
The method of claim 1 , wherein the predetermined number comprises:
and the value is determined to be greater than or equal to the number of non-zero elements included in the columns of the reference matrix.
3. The method of claim 2, wherein the predetermined number comprises:
A value obtained by multiplying the number of non-zero symbols by the maximum number of accessible terminals is determined to be greater than or equal to a value obtained by dividing the code length by the code length, and the number of columns of the transmission matrix is,
and corresponding to a value obtained by multiplying the code length by the predetermined number.
The method of claim 1, wherein the reference sequence comprises:
A baseband zadoff-chu (ZC) sequence, wherein the ZC sequence is
and a length having a number equal to the predetermined number.
A method for receiving a reference signal in a communication system, comprising:
Receiving the reference signal generated based on a transmission matrix,
The transmission matrix is generated by repeating a reference matrix including zero elements and non-zero elements by a predetermined number, and the reference sequence includes the non-zero elements included in the transmission matrix. - assigned to zero elements,
One of the plurality of elements included in the reference matrix is allocated to each of the non-zero elements included in a first column in the transmission matrix, and an element cyclically shifted from one element included in the reference sequence is the first column and each non-zero element included in the second column in the transmission matrix positioned at a predetermined column interval from .
The method of claim 6, wherein the reference matrix is
The code length used in the communication system, the number of non-zero symbols, the maximum number of accessible terminals in the communication system, the number of elements included in rows of the reference matrix corresponding to the code length, and the maximum accessible terminal The signal receiving method, characterized in that generated based on the number of elements included in the columns of the reference matrix corresponding to .
7. The method of claim 6, wherein the predetermined number comprises:
and a value greater than or equal to the number of non-zero elements included in the columns of the reference matrix is determined.
8. The method of claim 7, wherein the predetermined number comprises:
A value obtained by multiplying the number of non-zero symbols by the maximum number of accessible terminals is determined to be greater than or equal to a value obtained by dividing the code length by the code length, and the number of columns of the transmission matrix is,
and corresponding to a value obtained by multiplying the code length by the predetermined number.
The method of claim 6, wherein the reference sequence comprises:
A baseband zadoff-chu (ZC) sequence, wherein the ZC sequence is
and a length having a number equal to the predetermined number.
An apparatus for transmitting a reference signal in a communication system, comprising:
At least one processor that controls to transmit a reference signal generated based on a transmission matrix, and transmits the reference signal,
The transmission matrix is generated by repeating a reference matrix including zero elements and non-zero elements by a predetermined number, and the reference sequence includes the non-zero elements included in the transmission matrix. - assigned to zero elements,
One of the plurality of elements included in the reference matrix is allocated to each of the non-zero elements included in a first column in the transmission matrix, and an element cyclically shifted from one element included in the reference sequence is the first column and allocated to each of the non-zero elements included in the second column in the transmission matrix positioned at a predetermined column interval from .
The method of claim 11, wherein the reference matrix is
The code length used in the communication system, the number of non-zero symbols, the maximum number of accessible terminals in the communication system, the number of elements included in rows of the reference matrix corresponding to the code length, and the maximum accessible terminal The signal transmission apparatus, characterized in that generated based on the number of elements included in the columns of the reference matrix corresponding to the.
12. The method of claim 11, wherein the predetermined number comprises:
and a value greater than or equal to the number of non-zero elements included in the columns of the reference matrix.
13. The method of claim 12, wherein the predetermined number comprises:
A value obtained by multiplying the number of non-zero symbols by the maximum number of accessible terminals is determined to be greater than or equal to a value obtained by dividing the code length by the code length, and the number of columns of the transmission matrix is,
and a value obtained by multiplying the code length by the predetermined number.
The method of claim 11, wherein the reference sequence comprises:
A baseband zadoff-chu (ZC) sequence, wherein the ZC sequence is
and a length having a number equal to the predetermined number.
An apparatus for receiving a reference signal in a communication system, comprising:
At least one processor that controls to receive the reference signal generated based on a transmission matrix, and receives the reference signal,
The transmission matrix is generated by repeating a reference matrix including zero elements and non-zero elements by a predetermined number, and the reference sequence includes the non-zero elements included in the transmission matrix. - assigned to zero elements,
One of the plurality of elements included in the reference matrix is allocated to each of the non-zero elements included in a first column in the transmission matrix, and an element cyclically shifted from one element included in the reference sequence is the first column and each non-zero element included in the second column in the transmission matrix positioned at a predetermined column interval from .
The method of claim 16, wherein the reference matrix comprises:
The code length used in the communication system, the number of non-zero symbols, the maximum number of accessible terminals in the communication system, the number of elements included in rows of the reference matrix corresponding to the code length, and the maximum accessible terminal The signal receiving apparatus, characterized in that generated based on the number of elements included in the columns of the reference matrix corresponding to the.
17. The method of claim 16, wherein the predetermined number comprises:
and a value greater than or equal to the number of non-zero elements included in the columns of the reference matrix.
18. The method of claim 17, wherein the predetermined number comprises:
A value obtained by multiplying the number of non-zero symbols by the maximum number of accessible terminals is determined to be greater than or equal to a value obtained by dividing the code length by the code length, and the number of columns of the transmission matrix is,
and a value obtained by multiplying the code length by the predetermined number.
The method of claim 16, wherein the reference sequence comprises:
A baseband zadoff-chu (ZC) sequence, wherein the ZC sequence is
and a length having a number equal to the predetermined number. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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